Ferroelectric and other chiral liquid crystal compounds have been disclosed in WO 96/00710 A1, EP 0 339 414 A2, EP 0 360 042 A1, EP 0 306 195 A2, GB 2 200 912 A, U.S. Pat. No. 7,022,259, U.S. Pat. No. 5,494,605, U.S. Pat. No. 5,382,380, U.S. Pat. No. 5,250,222, U.S. Pat. No. 4,419,264, WO 89/02425 A1, EP 0 329 153 A2, U.S. Pat. No. 5,486,309 A, U.S. Pat. No. 5,358,663 A and U.S. Pat. No. 4,780,241.
However, the compounds of the prior art are not yet fully satisfactory and do not meet all of the requirements for the applications in ferroelectric and cholesteric liquid crystalline displays as mentioned supra. Especially, compounds are needed that will allow the production of shock-stable ferroelectric liquid crystal displays as well as at the same time fast switching, low operating voltage monostable or bistable chiral nematic LCDs. In the context of the present invention, it is understood that the designations “cholesteric” and “chiral nematic” are deemed equivalent.
In U.S. Pat. No. 4,419,264, a few nonchiral fluorine-containing 4,4-bis-(cyclohexyl)-biphenyl derivatives are disclosed which can be used as the components of nematic liquid crystal mixtures (examples 3 to 5). While it is mentioned that R1 or R21 can be branched (and therefore chiral), there is no information about such chiral compounds, their properties and the properties of the liquid crystal mixtures based upon them. It is clear from the description of U.S. Pat. No. 4,419,264 that these compounds cannot be used for the preparation of                cholesteric liquid crystal mixtures with a wide temperature range of the cholesteric phase (from −30° C. up to 100° C.), good dynamic parameters (with a response time of less than 5 ms or 10 ms), low threshold and saturation voltages (less than 20 V), good sharpness of the electro-optical curve, and good mechanical, thermal and long-term stability of bistable textures, and of        ferroelectric liquid crystal mixtures with different values of the optical anisotropy (Δn) and the spontaneous polarisation, or chiral nematic mixtures with different values of a helical pitch and an optical anisotropy (Δn), a positive or negative dielectric anisotropy (Δ∈), a needed value of the elastic constants (especially K22) and a wide temperature range of the ferroelectric or cholesteric phases.        
The compounds and liquid crystal mixtures of U.S. Pat. No. 4,419,264 do not allow in combination with alignment materials to create shock-stable ferroelectric liquid crystal displays LCDs with low operating voltage and high contrast ratio, or fast switching, low operating voltage monostable or bistable chiral nematic LCDs.
And finally, the chiral compounds of U.S. Pat. No. 4,419,264 cannot be really used for the practical application. The synthetic routes to such compounds, in contrast to the compounds of present invention and the non-chiral compounds of U.S. Pat. No. 4,419,264, are multistage and the final yield of these compounds is very low. Additionally, it should be noted that the starting materials: chiral 4-alkylcyclohexanones, the Grignard reagents etc. are very difficult to prepare.
In WO 89/02425 A1, only a few chiral fluorine-containing terphenyls and nonchiral quaterphenyls are disclosed, which compounds can be used as components of ferroelectric liquid crystal mixtures (see examples 12 and 13, and 14 to 24). There is no information about chiral quaterphenyls, their properties and the properties of the liquid crystal mixtures based upon them.
In EP 0 329 153 A2 and in WO 96/00710 A1, lactic derivatives and chiral cyclohexyl derivatives are disclosed which are different from compounds of formula (1), form liquid crystal phases only in a narrow temperature range, and which have properties which do not allow to use them for the preparation of                cholesteric liquid crystal mixtures with a wide usable temperature range of the cholesteric phase (from −30° C. up to 100° C.), good dynamic parameters (with a response time of less than 5 ms or 10 ms), low threshold and saturation voltages (less than 20 V), good sharpness of the electro-optical curve, and good mechanical, thermal and long-term stability of bistable textures, and of        ferroelectric liquid crystal mixtures with different values of the optical anisotropy (Δn) and the spontaneous polarisation, or chiral nematic mixtures with different values of a helical pitch and an optical anisotropy (Δn), a positive or negative dielectric anisotropy (Δ∈), a needed value of the elastic constants (especially K22) and a wide temperature range of the ferroelectric or cholesteric phases.        
The compounds and liquid crystal mixtures of EP 0 329 153 A2 and WO 96/00710 A1 do not allow in combination with alignment materials to create the shock-stable ferroelectric liquid crystal displays (LCDs) of this invention with low operating voltage and high contrast ratio, or fast switching, low operating voltage monostable or bistable chiral nematic LCDs.
Similarly, in U.S. Pat. No. 5,494,605 A, U.S. Pat. No. 5,382,380 A, EP 0 360 042 A1, GB 2 200 912 A, EP 0 306 195 A2, U.S. Pat. No. 5,486,309 A, and U.S. Pat. No. 5,358,663 A, chiral terphenyls, 2,5-diphenyl-pyridines and other compounds are disclosed, which do not fall under the general formula (1).
4-Pentyl-3″-chloro-4′″-(2-methylbutyloxy)quaterphenyl described before forms Sm C* phase at high temperature and in a narrow temperature range and has a low spontaneous polarisation, which does not allow to use this compound for the preparation of shock-stable ferroelectric liquid crystal displays LCDs with low operating voltage, high contrast ratio and a wide temperature range of Sm C* phase.
For the reasons given above, the chiral esters of 4-decyloxy-3″-methyl-4″-quaterphenyl carboxylic acid as described therein cannot be used for the preparation of shock-stable ferroelectric liquid crystal displays (LCDs) with low operating voltage, high contrast ratio and a wide temperature range of Sm C* phase. These compounds do not form a Sm C* phase. And additionally, the synthetic routes to these compounds, in contrast to those leading to the compounds of present invention are multistage, and preparation and purification of the intermediate, 4-decyloxy-3″-methyl-4′″-quaterphenyl carboxylic acid and the final products are complicated to make.
It should be noted that the chiral compounds of WO 96/00710 A1, EP 0 339 414 A2, EP 0 360 042 A1, EP 0 306 195 A2, GB 2 200 912 A, U.S. Pat. No. 7,022,259, U.S. Pat. No. 5,494,605, U.S. Pat. No. 5,382,380, U.S. Pat. No. 5,250,222, U.S. Pat. No. 4,419,264, WO 89/02425 A1, EP 0 329 153 A2, U.S. Pat. No. 5,494,605 A, U.S. Pat. No. 5,486,309 A, U.S. Pat. No. 5,358,663 A and U.S. Pat. No. 4,780,241, opposite to the compounds of formula (I), do not have a such rigid rod shape central core of the molecules and do not form the smectic C phase in the overall temperature range of from 10° C. to 154° C. These compounds are characterised by the conformation changes of the fragments of the molecules, and the strong dependence of these changes upon the temperature, pressure etc., which do not allow to use them for the preparation of shock-stable ferroelectric or monostable or bistable chiral nematic LCDs with low operating voltage and high contrast ratio.
Low power consumption, fast response time as well as pixel bistability, when the devices have two or more stable states without field, are further desirable attributes for LCDs. Bistable chiral nematic devices such as those described in U.S. Pat. No. 6,928,271 B2, and WO 2004/104980 A2 can be driven line-by-line—once displayed—the information is stored while updating the rest of the screen, and simple matrix addressing may be employed.
However, well-known chiral compounds do not allow to obtain liquid crystal mixtures with a wide usable temperature range of the cholesteric phase (from −30° C. up to 100° C.), good dynamic parameters (with a response time of less than 5 ms or 10 ms), low threshold and saturation voltages (less than 20 V), good sharpness of the electro-optical curve, and good mechanical, thermal and long-term stability of bistable textures.
Ferroelectric liquid crystals (FLCs) are also interesting candidates for active materials in future display devices. FLCs exhibit a fast response, a wide viewing angle and bistable memory capability and have been considered for light shutter and display applications. Ferroelectric liquid crystals displays (FLCDs) are characterised by high-speed operation, in-plane switching and ultra-high resolution.
However, technical issues on the zig-zag defects, mechanical stability and DC voltage balance still hinder FLCDs from widespread applications. The zig-zag defects tend to deteriorate the electro-optic (EO) properties of the devices, while the mechanical and shock-sensitive FLC alignment and residual voltage would cause concerns for long-term stability. It is hard to fabricate defect-free FLCDs owing to the appearance of the zig-zag defect that degrades memory capability and contrast ratio of the display (S. T. Lagerwall, Ferroelectric and Antiferroelectric Liquid Crystals, Wiley-VCH, Weinheim and New York, 1999)
There are other problems with FLCDs, including high driving voltages (from 20 V to 40 V), a low cell gap (under 2 μm), no greyscale, a paucity of stable, room-temperature materials, and wide temperature range materials, and structural defects in the display cells which result from thermal and mechanical stress because of non-optimised FLC materials and alignment conditions.